1. Field of the Invention
The present invention relates to manually operated motor throttles and particularly to rotating throttle assemblies for mounting on a vehicle handle bar. The rotating throttle assembly of the present invention provides smooth action, reduced rotational range required to fully open the throttle, and a balanced dual post cable pull attached to the throttle cable.
2. Description of the Prior Art
Motor driven vehicles, such as motorcycles, snowmobiles, and jet skis are typically operated by an individual straddling the vehicle and steering with a rotatable handle bar system. Handle bar systems generally comprise two outwardly extending members, one on each side of the vehicle. The members each have a proximal end joined to a stem which extends downward and connects to a steering system. The members each have a distal end covered by a hand grip. The operator grasps one hand grip in each hand and rotates the handle bar, using both hands simultaneously, to turn the vehicle.
It is a conventional design feature to install the motor throttle assembly at the distal end of one of the handle bar members and to configure the throttle to operate by manual rotation of one of the hand grips. The operator may adjust the throttle to control motor speed while maintaining a two handed grip on the handle bar, for steering. Typically, a flexible wire cable is connected to the throttle linkage of the motor, directed by a conventional cable housing to an opening in the handle bar system and led internally to the distal end of one handle bar member, where it may be connected to the throttle assembly.
The throttle assembly comprises an inner sleeve mounted on the handle bar member. Set screws are typically used to retain the inner sleeve on the distal end of the handle bar member. A generally cylindrical cable pull is attached to the cable end and disposed within the inner sleeve. A guide post is mounted on a pin fixed to a side of the cable pull. The guide post is designed to slidably rest within and protrude outward through an elongate longitudinal cutout provided in the inner sleeve. An outer sleeve is provided with an inside diameter slightly larger than the outside diameter of the inner sleeve and the outer sleeve receives the inner sleeve in close fitting and rotatable engagement. The outer sleeve is provided with an elongate longitudinally extending helical cutout designed to receive the protruding portion of the guide post.
A threaded cup is inserted into the outer sleeve and is turned to engage a mating set of threads provided on the inner sleeve. A flange is provided at an intermediate position within the outer sleeve to act as a stop for the threaded cup. Tightening the threaded cup retains the inner sleeve within the outer sleeve. Rotating the outer sleeve urges the guide post along the helical cutout and causes the cable pull to traverse the length of the longitudinal cutout thereby pulling the cable and accelerating the motor.
As the outer sleeve rotates, the relative movement of the helical cutout with respect to the longitudinal cutout applies a resultant force urging the guidepost in a direction parallel to the longitudinal axis of the inner sleeve. The force, which is transmitted through the guide post to the cable pull is unbalanced with regard to the direction of motion, and tends to turn the cable pull sideways during the traverse of the inner sleeve. The frictional force generated at points of contact between the cable pull and the inner sleeve increases with increasing cable tension, producing a non-linear response in the throttle mechanism.
There is a need for a motor throttle assembly designed to apply a balanced force to the cable pull to limit sideways movement, for reducing friction between the cable pull and the inner sleeve and for limiting play in the throttle cable. There is a need for a throttle assembly having means for mounting on a handle bar without requiring set screws. There is a need for a throttle assembly having smooth action, and requiring reduced rotation to fully open the throttle.